Tectonostratigraphic evolution of the Paleogene basins in North Pakistan: Implications for the timing of closure of Eastern Tethys and India-Asia Collision

Abstract

The current investigation's goal is to time the eventual closure of Pakistan's portion of the northern Tethys rim in Kohat-Potwar Basin by using integrated bio-sequence stratigraphy and facies information. The Paleogene strata is divided into six biozones while its depositional profile resembles a distally steepened-homoclinal platform. Paleogene deposits in the Kohat Basin include two depositional cycles, two transgressive-highstand systems tracts, one lowstand systems tract, and two sequence boundaries. Three transgressive-highstand systems tracts were observed in the Potwar Basin, which are separated by two tectonically controlled and one eustatic sequence boundary. The sequence boundaries in both basins are synchronous at 50–49.5 Ma and mark a period of drastic change in sediment character, which may have been caused by the combined effects of uplift and eustatic sea level fall. This suggests that the proto-closure of the northern rim of Tethys occurred between 50 and 49.5 Ma. Only the Kohat Basin experienced the restoration of marine conditions, which happened in the Middle Lutetian at around 45.8 Ma and may have been brought on by a combination of flexural loading of the Indian Plate and eustatic sea-level rise that persisted until the Kohat Basin's closure in the Upper Lutetian at around 41.2 Ma.